Kinases hexokinase

Kinases, see Adenylate kinase, Hexokinase, Phosphoglycerate kinase, Phosphofructokinase, or Pyruvate kinase Lactate dehydrogenase (Adams et al., 1970)... 

Exploration of Bulk Tolerance at ATP Sites. Non-covalent type inhibitors have also been used to study bulk tolerance around the ATP binding sites. In this vein Hampton and co-workers have both synthesized and tested as inhibitors a large number of adenine nucleotide analogs (Figure 2f) to probe the bulk tolerance at a number of positions on the parent compound (28-31) These compounds have been used to study systematically the isoenzyme selectivity of adenylate kinases, hexokinases, thymidine kinases and pyruvate kinases with respect to bulk tolerance at many sites on the ATP molecule. Some of the most isoenzyme specific results were obtained with pyruvate kinase isoenzymes K,L and M using ADP derivatives. Here 3 -0Me-ADP was found to inhibit pyruvate kinase preferentially with a ratio of inhibitory potency of 7.6 6.0 1.0 for the K,M and L isoenzymes, respectively. Another compound, 8-NHEt-ADP, was selective for the M isoenzyme, giving a ratio of 7.1 1.2 1.0 for the M, K and L forms, respectively. 

For fructose to enter the pathways of intermediary metabolism, it must first be phosphorylated (Figure 12.2). This can be accomplished by either hexokinase or fructokinase (also called ketohexo-kinase). Hexokinase phosphorylates glucose in all cells of the body (see p. 96), and several additional hexoses can serve as substrates for this enzyme. However, it has a low affinity (that is, a high Km, see p. 59) for fructose. Therefore, unless the intracellular concentration of fructose becomes unusually high, the normal presence of saturating concentrations of glucose means that little fructose is converted... 

Mg Polynucleotide phosphoryla.ee. ATPase. choline acylase, deoxyribonuclease, acetate kinase, adenosine phosphokinase, tructokinase. glyceric kinase, hexokinase Chlorophyll... 

ADP/ATP pyruvate kinase + hexokinase membrane with LDH+LMO O2 electrode 220 Wollenberger (1987b)... 

ATP pyruvate kinase + hexokinase + lactate dehydrogenase + lactate oxidase 2 reactors thermistor 1700 Kirstein et al. (1987)... 

Kinases Direct transfer of terminal phosphoryl group of ATP to substrate Creatine kinase Adenylate kinase Hexokinase Phosphoglycerate kinase Pyruvate kinase Protein kinase Myokinase Phosphofructokinase Type 1 (M-S-E) Type 1 Typel Type 1 Type 2 (S-M-E)... 

W. A. Blattler and J. R. Knowles (1979), Stereochemical course of phospho-kinases. The use of adenosine [y-(5 )- 0, 0, 0] triphosphate and the mechanistic consequences for the reactions catalyzed by glycerol kinase, hexokinase, pyruvate kinase and acetate kinase. Biochemistry 18, 3927-3933. 

The iPocp) folding unit occurs in many proteins. It is the essential structure of oc/p proteins, a common structure of dehydrogenases (alcohol dehydrogenase, lactate dehydrogenase), some kinases (hexokinase, adenylate kinase, phosphoglycerate kinase), and phosphoglycerate mutase. It is also found in carbonic anhydrase, carboxypeptidase A, cytochrome 65, flavodoxin, papain, rhodanese, thioredoxin, and subtilisin. 

In most animal, plant, and microbial cells, the enzyme that phosphorylates glucose is hexokinase. Magnesium ion (Mg ) is required for this reaction, as for the other kinase enzymes in the glycolytic pathway. The true substrate for the hexokinase reaction is MgATP. The apparent K , for glucose of the animal... 

Figure 5.3 Major control points of glycolysis and the TCA cycle. Enzymes I, hexokinase II, phosphofructokinase III, pyruvate kinase IV, pyruvate dehydrogenase V, citrate synthase VI, aconitase VII, isocitrate dehydrogenase VIII, a-oxoglutarate dehydrogenase.

Glycolysis is regulated by three enzymes catalyzing nonequilibrium reactions hexokinase, phosphoffuc-tokinase, and pyruvate kinase. 

Mechanism for Gluconeogenesis. Since the glycolysis involves three energetically irreversible steps at the pyruvate kinase, phosphofructokinase, and hexokinase levels, the production of glucose from simple noncarbohydrate materials, for example, pyruvate or lactate, by a reversal of glycolysis ( from bottom upwards ) is impossible. Therefore, indirect reaction routes are to be sought for. 

Many assays have been described in which the initial product forms the substrate of an intermediary reaction involving auxiliary enzymes. The assay of creatine kinase (EC 2.13.2), for example, involves hexokinase (EC 2.7.1.1) as the auxiliary enzyme and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) as the indicator enzyme ... 

Treatment of 9-(/ -D-ribofuranosyluronic acid)adenine with diphenylphosphoro-chloridate and orthophosphate or tripolyphosphate yields (62) and (63), which, although unstable, inhibit rabbit AMP aminohydrolase and pyruvate kinase, respectively, with behaviour characteristic of active-site-specific reagents.98 Adenylate kinases from several sources are inactivated by iV6-[2- and 4-fluorobenzoyl]-adenosine-5 -triphosphates, with kinetics characteristic of active-site labelling, although these compounds were without effect on yeast hexokinase and rabbit pyruvate kinase.99... 

Where are the control points Reactions catalysed by. Hexokinase/Glucokinase Phosphofructokinase Pyruvate kinase... 

Genetically-determined deficiency of G6PD is the most common cause of haemolysis arising from enzyme defects. Mutated glycolytic enzymes such as hexokinase, phosphofructokinase, aldolase and pyruvate kinase can also bring about haemolysis but the occurrence of these defects are much rarer than for G6PD deficiency (see Case N otes at the end of this chapter). 

GNG exploits the fact that most of the reactions of glycolysis are reversible so the enzymes are shared between the two pathways. There are three kinase reactions (glucokinase/hexokinase, PFK and pyruvate kinase), which are not physiologically reversible are therefore the problem steps in the synthesis of glucose these three steps are overcome using alternative enzymes (Table 6.5, see also Section 1.7.1). 

Arabinose-binding protein domains 1 and 2 Dihydrofolate reductase Adenylate kinase Rhodanese domains 1 and 2 Glutathione reductase domains 1 and 2 Phosphoglycerate mutase Phosphoglycerate kinase domain 2 Pyruvate kinase domain 3 Hexokinase domains 1 and 2 Catalase domain 3 Aspartate aminotransferase... 

Hexokinase Pyruvate kinase Adenylate kinase Phosphoglycerate kinase Phosphofructokinase Protease inhibitors Pancreatic trypsin inhibitor Soybean trypsin inhibitor Streptomyces subtilisin inhibitor Nucleases... 

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